Field of the Invention
The present invention relates of a device for detecting an erroneous signal characteristic of a load on an internal combustion engine and, more particularly, to a device comprising a first and second load signal generating means and means for recognizing whether or not the first and second load signal are characteristic of the same measured load value.
In the course of determining an essential measurement value it may become necessary to employ two sensor systems, which operate independently of each other, for the determination. It is then possible by means of such redundant systems to detect an error by means of a comparison of the signals provided by the sensor systems, for example if a signal exceeds an upper threshold value or falls below a lower threshold value.
However, it is also further possible to compare both signals and to monitor, for example, the distance between two signals in order to detect an error if the difference between the two signals exceeds a threshold value. Such a plausibility check is performed in DE-OS 43, 44 633, for example.
With this known plausibility check, the so-called main load signal and the so-called secondary load signal are compared with each other in connection with the load registration in an internal combustion engine. Here, the main load signal is determined by directly registering the air flow aspirated by the internal combustion engine with the aid of an air flow sensor. The registration of the main load signal can also be performed indirectly with an induction pipe pressure sensor. In the course of this, the aspirated quantity of fresh air is calculated, using the gas equation and taking into consideration the temperature of the aspirated air, the remaining gas portion and the cylinder stroke volume. The secondary load signal is formed in both methods (pressure sensor, or respectively air flow sensor) by evaluating the rpm and the angular position of the throttle of the internal combustion engine, for example with the aid of a throttle potentiometer. The main load signal as well as the secondary load signal must correspond to each other to a large extent when the air flow sensor or the pressure sensor, or respectively the throttle potentiometer operate correctly and are optimally matched. However, if deviations nevertheless occur, it is possible to conclude that one of the two sensor systems is in error.